I can personally attest to the fact that Tumblr has become one of the best places to find out about new art and photography. The problem is weeding the chaff from the grain because images and content is often "reblogged" by some people who have no regard for crediting sources or creators. So, you might come across an image of something that you are intrigued by and the photo link only leads to someone's "themed" Tumblr, with no link(s) to the source, where you might get more info about said image.

This list of some of the better art and photography blogs on the site put together by one of the editors of BOOOOOOOM! focuses on those Tumblr blogs that retain creator credits and source links...